DE102005011395A1 - Hydraulic control arrangement - Google Patents

Abstract

The hydraulic control device has a pressure regulator (32) pressurized by a constant force (Px) in the opening direction, lower pressure in closing direction downstream of the inlet metering orifice (40,44) and upstream of outlet metering orifice (42,46). The discharge flow of the pump (8) is adjustable as a function of larger of the two pressures.

Description

The The invention relates to a hydraulic control arrangement for driving a consumer according to the generic term of claim 1

From the DE 100 45 404 C2 a control arrangement is known in which a hydraulic consumer, for example a double-acting cylinder for moving a load via a continuously adjustable directional control valve with pressure medium can be supplied. In the pressure medium inlet to the cylinder and in the drain from the cylinder each unlockable check valves are provided, wherein the inlet-side check valve is brought by the pressure downstream of the directional control valve in an open position. The drain-side check valve can be moved by pressing a poppet into an open position, which allows the drainage of the pressure fluid from the consumer to the directional control valve. In this solution, via the drain-side blocking block is a flow control by feedback of the discharge pressure before determining the course Schiebersteuerkante the continuously adjustable directional valve on the topping piston of the blocking block.

In the DE 199 31 142 C2 a control arrangement is disclosed in which a supply control via an upstream of the control valve individual pressure compensator. This is acted upon in the opening direction by the force of a spring and the pressure in the inlet to the consumer.

The DE 36 39 174 C2 shows a control arrangement for a single-acting hydraulic consumer, wherein a continuously variable directional control valve LS-pressure compensator is connected upstream, which is acted upon in the closing direction by the force of a spring and the individual load pressure and in the opening direction of the pressure between the pressure compensator and the directional control valve. The known control arrangement further has a load-compensated unlockable check valve, via which a sequence control can be performed.

In the DE 102 16 958 a hydraulic control arrangement is shown, in which upstream of a Zulaufmessblende an LS-pressure compensator is provided, which is acted upon in the opening direction by the force of a spring and the highest pressure downstream of the Zulaufmessbrende and upstream of a drain metering orifice. In the closing direction, the LS pressure compensator acts on the pressure upstream of the inlet orifice plate.

All vorbeschiebenen embodiments have the disadvantage in common that the inlet cross section and the flow cross section the measuring orifice-defining control edges (inlet control edge, flow control edge) extremely accurate must be coordinated.

adversely in these solutions Furthermore, that is only either the consumer inflowing pressure medium flow or the expired by the consumer Volume flow independent of load can be controlled. About that In addition, especially occurs in the control of double-acting Cylinders at so-called pulling loads - ie at loads in which the pressure in the drain higher as is in the inflow - the Risk of undersupply of the inlet-side cylinder chamber. Such a deficiency can lead to cavitation, by the consumer or the associated hydraulic switching elements to be damaged. Such Betriebszustend can, for example, in a downhill or occur when a load is first lifted, then one Dead center overcomes and subsequently pulling on the hydraulic consumer acts.

to Avoiding such underpayments of the consumer, for example Suction valves are used. Due to the comparatively low Differential pressure between the suction side and the tank pressure when vacuuming must this Valves, however, a very large cross-section exhibit.

A alternative possibility consists in providing biasing valves in the pressure fluid outlet. However, such bias valves go with a high energy loss This is because the inlet pressure, especially at low loads, strong must be raised.

A another possibility is to use brake valves. However, these also need a comparatively high pressure on the inlet side around the volume flow to control on the drain side and thus a shortage of the feed to avoid.

D. h., these known possibilities to avoid an undersupply (suction valve, preload valve, Lowering brake valve) require a considerable circuit engineering Effort and are about it also associated with energy losses.

In contrast, the present invention seeks to provide a hydraulic control arrangement for controlling a consumer, by which a shortage can be avoided with little effort and at the pressure medium flow to the consumer and the from Consumer running pressure medium flow rate can be controlled independent of load.

These Task is by a hydraulic control arrangement with the features of claim 1.

The inventive hydraulic Control arrangement is with an adjustable inlet and an adjustable Drain gauge is running, wherein a arranged in the pressure medium flow pressure compensator in the opening direction from a constant force and in the closing direction from the lower of the pressures downstream the inlet orifice and upstream of the drain metering diaphragm acted upon is. In the pressure fluid outlet a lockable blocking block is provided, in the inlet direction as a check valve acts and in the pressure fluid outlet the drain pressure medium volume flow regulates.

By the interaction of the pressure balance and the load-compensated blocking block can both the consumer as well as the consumer Pressure fluid volume flows independently be kept constant by the load pressure. About it can over the pressure balance and the Locking block of the consumers are biased in all operating conditions, so that the initially mentioned undersupply in the pressure medium feed safely avoided.

The Preload the consumer can easily by adjusting on the pressure compensator in the opening direction acting constant force to be adjusted to the system.

The inventive solution can be realize with very little effort, the above-described additional Valve arrangements, such as Nachsaug valves, preload valves, lowering brake valves etc. not needed become. Due to the bias of the consumer can eliminate air Reliably avoided on the suction side become.

It showed, furthermore, that in the hydraulic Control arrangement requires a smaller increase in the inlet pressure is so opposite usual solutions enables energy savings is.

at a particularly preferred embodiment The invention is a delivery a pump of the hydraulic control arrangement in dependence from the larger of the pressures downstream of the Inlet orifice and upstream the drain gauge is controlled. This flow rate is regulated in this way, in that in the pump line to a certain pressure difference Ap over the Load pressure lying pump pressure applied (LS system).

The Inlet and drain orifice plates are preferably continuous adjustable directional control valve whose working connections to an intake and a drain line are connected and its pressure port connected to a flow line and the tank connection to a return line is.

The inventive solution makes it possible the controlled by an inlet control edge on inlet cross section greater than the on a flow control edge on controlled flow cross-section perform or the drain cross-section later aufzusteuern, so that due to the lower requirements at the Inlet control edge simplifies the vote of the two control edges is. The speed of the consumer is then always through the Outlet cross section determined.

The on the pressure compensator acting constant force is in a variant of the invention by a on a control surface of a pressure compensator piston acting control pressure applied. Alternatively, the constant Force too over a spring or the like applied to the pressure compensator piston become.

The Adjusting the preload of the consumer can then be easy Be changed way by adjusting the constant pressure. This one can too be lowered to zero by suitable circuitry, so that the Pressure fluid can flow from the consumer, without the pressure medium promoted to the inlet becomes.

at Control of a double-acting consumer, for example a differential cylinder are preferably both in the inlet as well as in the course unlockable blocking blocks provided, each an actuable by a control pressure topping piston to have. The structure of the control arrangement is particularly simple when this control pressure corresponds to the constant control pressure of the pressure compensator in the opening direction applied.

Of the smaller pressure downstream the inlet orifice and upstream of the drain orifice plate can via a Inverse shuttle valve can be tapped.

other advantageous developments of the invention are the subject of further Dependent claims.

in the The following is a preferred embodiment of the invention explained with reference to a single figure. This shows a circuit diagram of a hydraulic control arrangement for controlling a double-acting consumer.

Such control arrangements are used in particular for controlling the consumers of a mobile implement, for example in a forklift or a tractor. In the illustrated embodiment, the consumer is a differential cylinder 2 executed, via a valve assembly 4 with a pressure medium supply 6 is connectable.

The pressure medium supply 6 has in the illustrated embodiment, a constant pump 8th sucked via the pressure fluid from a tank T and into a pump line 10 is encouraged. From the pump line 10 branches a bypass line 12 in which an inlet pressure compensator 14 is arranged, in the opening direction of the pressure in the pump line 10 and in the closing direction of the highest load pressure of all consumers and the force of a spring 16 is charged. This highest load pressure is tapped in a known manner via a shuttle valve cascade of all consumers of the system and is located on a load reporting line 18 at the inlet pressure balance 14 at. The pump 8th can be designed as a fixed displacement pump with speed-controlled drive or as a variable displacement pump.

The cylinder 2 backflowing pressure fluid flows depending on the direction of movement of the cylinder 2 via a return line 20 or a return line 22 back to tank T.

The valve assembly, which is designed for example as a valve disc of a mobile control block, has a pressure port P, a LS port LS, two return ports R and two working ports A, B, the latter via working lines 24 . 26 with a bottom-side cylinder chamber 28 or a piston rod side annulus 30 are connected.

As the figure further shows, the two return lines 20 . 22 with the two return connections R, the pump line 10 with the pump connection P and the load signaling line 18 connected to the LS port LS. The valve assembly consists essentially of a pressure compensator, hereinafter individual pressure compensator 32 called, indicated by dash-dotted lines continuously adjustable directional control valve 34 and two unlockable blocks 36 . 38 , The continuously adjustable directional valve 34 usually has a direction of pressure fluid flow direction specifying part and a speed part, which is formed in each case by an inlet and a drain metering orifice. In the circuit diagram shown four measuring orifices are shown schematically, but depending on the setting of the directional part only two orifices are effective. D. h., At a pressure fluid flow to the working port A acts with the reference numeral 40 provided metering orifice as a metering orifice, while the drain metering orifice with the reference numeral 42 is provided, which is effective at a pressure fluid flow from the working port B to the tank T. Upon rotation of the flow direction, the measuring orifices, which are furthermore shown, then serve as inflow orifice 44 and as a flow meter 46 effective. The two drainage orifice plates 42 . 46 are each in a return channel 48 respectively. 50 arranged, which are each connected to one of the return ports R.

The directional valve has two working ports A 'and B', which via a supply line 52 and a drain line 54 connected to the working ports A, B. The structure of the blocking blocks 36 . 38 is known per se, so that detailed explanations are unnecessary. These blocks 36 . 38 can be by means of a pounding piston 56 respectively. 58 from a spring-biased Grundpositi on, in which they each act as a check valve in a flow position bring the back flow of the pressure medium from the cylinder 2 allows. The operation of the pounding piston 56 . 58 occurs via a constant control pressure p _x , which is tapped from a suitable control pressure supply. In the opposite direction acts on an annular surface of the pounding piston 58 the pressure (seen in the outflow direction) downstream of the respective blocking block 36 . 38 that has a channel 60 respectively. 62 from the inlet channel 52 or from the drainage channel 54 is tapped. Due to this feedback of the load pressure in the sequence, the blocking block operates 36 . 38 load compensated and regulates the pressure in the respective associated line, which then acts as a flow channel load-independent to a constant value. The blocking block, which is in each case in the inlet, then works as a check valve.

In a to the pressure port P of the valve assembly 4 connected feed channel 64 is the individual pressure balance 32 arranged in the opening direction of the constant control pressure p _x and in the closing direction of the force of a pressure compensator spring 66 and from a pressure in a message channel 68 is charged. This pressure is the smaller of the pressures in the inlet channel 52 and in the drainage channel 54 that is, the smaller of the pressures downstream of the inlet orifice 40 and upstream of the drain metering orifice 42 (At a pressure medium flow in the direction of the working port A and from the working port B to the tank T). This pressure is from the inlet channel 52 and from the drainage channel 54 each with a tap channel 70 . 72 tapped, each to an input of an inverse shuttle valve 74 to lead. Its output is to the signaling channel 68 connected.

From the tap channels 70 . 72 branches each one LS branch channel 76 . 78 off, each with a Input of a shuttle valve 80 whose output is connected to the input of another LS shuttle valve 82 the above-mentioned LS Wechselventilkasskade is connected, via which the highest load pressure of all of the pump 8th supplied consumers. This highest load pressure is then in the load reporting line 18 and acts on the slider of the inlet pressure compensator 14 in the closing direction.

For a better understanding of the invention will now be the function of the control arrangement according to the invention on the basis of the extension of the cylinder 2 explained, that is, the pressure medium is from the pump 8th via the working connection A into the cylinder chamber 28 promoted and out of the annulus 30 pushed back over the working port B to the tank T. The measuring aperture works 40 as inflow orifice and the orifice plate 42 as flow meter, the metering orifices 44 . 46 are closed.

principal function

To extend the cylinder 2 becomes the directional valve 34 adjusted so that an inlet control edge of the directional control valve 34 the cross section of the inlet measuring aperture 40 controls and accordingly a flow control edge of the cross section of the flow meter 42 opens. The directional valve 34 is designed so that the opening cross-section of the inlet orifice plate 40 is greater than that of the drain meter. The pressure medium then flows through the pressure compensator 32 , whose function will be explained in more detail below, the open-loop orifice plate 40 , the inlet channel 52 and acting as a check valve blocking block 36 , via the work connection A and the work line 24 in the cylinder room 28 , Accordingly, the pressure medium from the annulus 30 displaces and flows over the work line 26 , the working port B and the control block controlled by the constant control pressure p _x 38 , the drainage channel 54 pointing to controlled drain meter 42 , the return channel 50 , via the return connection R and the return line 22 back to the tank. The pressures in the inlet channel 52 and in the drainage channel 54 be via the inverse shuttle valve 74 as well as the shuttle valve 80 compared. The larger of the two pressures is via the shuttle valve 80 as LS signal to LS-change-over valve 82 and from there (if no other higher load pressure is present) to a closing direction effective control surface of the inlet pressure compensator 14 guided. The smaller of the two pressures is via the inverse shuttle valve 74 and the message channel 68 to the individual pressure balance 32 reported and compared there with the constant control pressure p _x . By means of this arrangement, the pressure medium volume flow through the inlet channel 52 via the inlet orifice 40 adjusted so that in front of the drain meter 42 aufsteuernden flow control edge in the flow channel 54 a constant pressure is maintained. If the smaller pressure picked up via the inverse shuttle valve is greater than the constant pressure p _x (minus the force of the compression balance spring 66 ), the pressure compensator damper of the individual pressure compensator throttles 32 the pressure medium flow stronger. If the via the inverse shuttle valve 74 tapped smaller pressure is too low, the flow opening of the individual pressure compensator 32 extended and correspondingly more pressure medium to inlet orifice 40 guided.

driven load

When the load is driven, the pressure in the inlet channel is 52 greater than the pressure in the discharge channel 54 , Apart from the pressure loss on the acting as a check valve blocking block 36 in the inlet, this larger pressure is passed as LS signal and the inlet pressure compensator 14 adjusted so that the pressure in the pump line 10 is a predetermined pressure difference .DELTA.p above this highest load pressure. The lower pressure on the drain side is to the individual pressure balance 32 reported and amounts to non-operated directional control valve 34 about 0 bar. The individual pressure balance 32 is then completely opened by the constant control pressure p _x . With actuated directional control valve 34 is over the pump 8th as long as pressure medium in the cylinder chamber 28 of the cylinder 2 promoted until the pressure on the drain side, ie in the drain channel 54 the value of the constant pressure p _x (minus the force of the pressure compensator spring 66 ) reached. The pressure balance slider of the individual pressure balance 32 reduces the opening cross section of the individual pressure balance, so that the pressure in front of the drain metering orifice 42 is kept constant.

When opening the drain meter 42 first, the pressure in the drainage channel drops 54 off, so the individual pressure compensator 32 something opens and the pressure medium flow through the inlet orifice 40 increases until the pressure in the drainage channel 54 reached the control pressure of the individual pressure balance again. The pressure medium volume flow on the inlet side is accordingly regulated so that the pressure in front of the drain metering orifice 42 constant on the control pressure of the individual pressure balance 32 remains. The opening cross section of the drain metering orifice 42 thus determines in conjunction with the control pressure of the individual pressure balance 32 the pressure medium volume flow. The cylinder 2 is clamped, this clamping force by suitable choice of the control pressure p _{x is} adaptable.

Pulling load

With pulling load, the pressure in the drainage channel 54 greater than the pressure in the inlet channel 52 , This pressure in the drainage channel 54 is via the load-compensated blocking block 38 held constant, this value is relatively low. This rule pressure of the blocking block 38 is called LS signal via the shuttle valves 80 . 82 to the pressure medium supply 6 delivered - the pressure in the pump line 10 is set to a comparatively low stand-by pressure.

On the inlet side, ie in the inlet channel 52 At first, there is only a very low or no pressure at a pulling load. This lower pressure is via the inverse shuttle valve 74 to the individual pressure balance 32 reported. This is when the directional control valve is not actuated 34 fully open. Now the directional valve 34 operated and the inlet orifice 40 controlled, the pump pressure is sufficient, the pressure in the inlet channel 52 so far raise that the individual pressure balance 32 is moved to a control position. If the pressure in the inlet reaches the control pressure of the individual pressure balance 32 , so this is controlled. In this way, the inlet-side pressure can be kept at a constant value, which is the control pressure of the individual pressure compensator 32 equivalent.

When opening the flow control edge, ie when controlling the drain orifice 42 the pressure in the drain channel becomes 54 through the load-compensated blocking block 38 from the load pressure in the annulus 30 or in the work management 26 to a constant level in the drainage channel 54 throttled and kept constant. Thus, the moving speed of the cylinder is also under pulling load through the opening cross section of the drain metering orifice 42 in conjunction with the control pressure of the load-compensated blocking block 38 certainly.

If the cylinder 2 is moved faster, initially decreases the pressure in the inlet channel with pulling load 52 From, according to also in the closing direction on the individual pressure compensator 32 reduces acting pressure so that this increases its opening cross-section until the pressure in the inlet (inlet channel 52 ) again the control pressure of the individual pressure balance 32 is reached. The cylinder 2 thus remains clamped even with pulling load with this control pressure.

By switching off the two blocking blocks 36 . 38 and the individual pressure balance 32 In the opening direction acting constant control pressure p _x , a safety function can be realized, since the two locking blocks 36 . 38 act as Rückschlagvenile and the individual pressure balance 32 is controlled. This safety function can be realized for example by a separate switching valve, via which the constant control pressure p _x can be switched off. This safety function can also be achieved by suitable design of the control edge of the directional control valve 34 be enabled.

If the constant control pressure only for the individual pressure balance 32 is turned off, so is a method of the cylinder 2 possible, without pressure medium is conveyed into the inlet chamber.

The constant control pressure p _x can be varied to the pressure drop across the control edges of the directional control valve 34 and thus to adapt the pressure medium volume flow for a given orifice aperture to different operating conditions.

Instead of the constant control pressure p _x and the pressure compensator spring 66 can also on the left side (view after the single figure) a spring are attached, via which a substantially constant force on the pressure compensator piston of the individual pressure compensator 32 is applied. Other means can be used to keep this force constant.

Disclosed is a hydraulic control arrangement for controlling a hydraulic Consumer with an adjustable inlet and an adjustable Drain meter and one arranged in a pressure medium flow Pressure compensator. The control arrangement further has a releasable Lock block, which acts as a check valve in the inlet direction and in Drain direction is unlocked by means of a control pressure. According to the invention, the pressure compensator in the opening direction from a constant force and in the closing direction from the lower of the pressures downstream of the Inlet orifice and upstream the drain metering diaphragm acted upon.

2

cylinder

4

valve assembly

6

Pressure medium supply

8th

fixed displacement pump

10

pump line

12

bypass line

14

Inlet pressure

16

feather

18

Load-sensing line

20

Return line

22

Return line

24

working line

26

working line

28

cylinder space

30

annulus

32

Individual pressure compensator

34

way valve

36

locking block

38

locking block

40

Supply measuring orifice

42

Drain measuring orifice

44

Supply measuring orifice

46

Drain measuring orifice

48

Return channel

50

Return channel

52

inlet channel

54

drain channel

56

topping

58

topping

60

channel

62

channel

64

forward channel

66

Compensator spring

68

signaling channel

70

Abgreifkanal

72

Abgreifkanal

74

inverse shuttle valve

76

Zweigkanal

78

Zweigkanal

80

shuttle valve

82

LS shuttle valve

Claims (10)

Hydraulic control arrangement for controlling a hydraulic consumer ( 2 ), with an adjustable inlet and an adjustable drain meter ( 40 . 42 ; 44 . 46 ), arranged in a pressure medium flow pressure compensator ( 32 ) for controlling the pressure medium volume flow via the inlet measuring diaphragm ( 40 . 42 ) and with at least one unlockable blocking block ( 36 . 38 ) which acts in the inlet direction as a check valve and in the flow direction by means of a control pressure (p _x ) is unlocked, characterized in that the pressure compensator ( 32 ) in the opening direction of a constant force (p _x ) and in the closing direction of the lower of the pressures downstream of the inlet orifice ( 40 . 44 ) and upstream of the drain metering orifice ( 42 . 46 ) is acted upon. Control arrangement according to claim 1, wherein a flow rate of a pump ( 8th ) is adjustable depending on the larger of the two pressures. Control arrangement according to claim 1 or 2, wherein the drain and inlet orifice ( 40 . 42 ; 44 . 46 ) by a continuously adjustable directional control valve ( 34 ) are formed. Control arrangement according to claim 3, wherein the is greater from an inlet control edge on controlled inlet cross-section as the flow-controlled by a flow control edge drainage cross section. Control arrangement according to one of the preceding claims, wherein the constant force is applied to a control surface of the pressure compensator ( 32 ) acting control pressure (p _x ) and / or is applied by a spring, Control arrangement according to claim 5, the first alternative, wherein the constant pressure (p _x ) is variable or lowered to zero. Control arrangement according to one of the preceding claims, wherein in the inlet and in the outlet in each case a releasable blocking block ( 36 . 38 ) is arranged, which a controllable by a control pressure Aufstoßkolben ( 56 ) Has. Control arrangement according to claim 7, wherein the poppet ( 56 ) is acted upon in the opposite direction to the control pressure from the pressure in the drain. Control arrangement according to claim 7 or 8, wherein the control pressure corresponds to the constant control pressure (p _x ). Control arrangement according to one of the preceding claims, wherein the smaller pressure via an inverse shuttle valve ( 74 ) is tapped.